The present invention provides a demulsifier which is both economical and efficient for use in breaking emulsion products, especially crude oil emulsions. This unique demulsifier comprises a vinyl polymer with a site capable of being alkoxylated, and at least one alkylene oxide selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, and the like. These demulsifiers are hereinafter referred to as alkoxylated vinyl polymers.
Crude oil emulsions, which are typically of the water-in-oil (w/o) variety, are formed when oil, water, and emulsifying agents (natural and man-made) are mixed together. The production process supplies adequate energy for the emulsification of crude oil.
Water-in-oil emulsions can be broken by chemical or physical methods, including heating, centrifugation and vacuum precoat filtration. Centrifugation breaks oil emulsions by separating oil and water phases under the influence of centrifugal force. Filtration of waste oil emulsions can be accomplished through high rate sand filters or diatomaceous earth filters. Chemical treatment of waste oil emulsion is directed toward destabilizing the dispersed water droplets and solids or destroying emulsifying agents. Acidification may be effective in breaking water-in-oil emulsions if the acid dissolves some of the solid material and thus reduces surface tension.
Recent techniques involve treatment of water-in-oil emulsions with a demulsifying agent containing both hydrophobic and hydrophilic groups that is able to form a water wettable adsorption complex. Because water droplets in oil tend to be positively charged, these types of emulsions are typically treated with an anionic (negative charge) organic emulsion breaker. Sometimes a combination of acid and organic emulsifying agents provide the best results.
Lately, several vinyl polymers demonstrated some potential as demulsifiers. Vinyl polymers offer potential advantages over conventional emulsion breakers. That is, manufacturing costs for vinyl polymers should be lower than that of traditional emulsion breakers, such as resin and alkoxylates. With the recent escalation in the price of ethylene oxide and potential for future price hikes, there is tremendous interest in the development of emulsion breakers which do not contain ethylene or propylene oxide. Unlike alkoxylation, vinyl polymerization does not require the use of a special reaction vessel. Important safety advantages are also associated with the formation of demulsifier intermediates which do not require the use of hazardous oxides.
The present inventor has discovered that in some cases the addition of small amounts of alkylene oxides, such as ethylene oxide, propylene oxide, and butylene oxide to vinyl polymers dramatically improves the performance of lower concentrations of vinyl polymers. Furthermore, the present inventor has discovered that alkoxylated vinyl polymers containing as little as 5% ethylene oxide worked well as a demulsifier in selected crude oils. The present inventor has found that alkoxylated vinyl polymers may be used in place of traditional resin or alkylene oxide demulsifiers, thereby substantially reducing the necessary oxide concentrations without affecting its emulsion breaking capability.
U.S. Pat. Nos. 4,626,379 (Buriks et al.), issued Dec. 2, 1986, and 4,582,628 (Buriks et al.), issued Apr. 15, 1986, demonstrate various types of vinyl polymers now in use. Burkis '379 discloses a demulsifier which comprises the partially condensed reaction product of a blend of at least two oxyalkylated materials with a vinyl monomer. Such oxyalkylated materials are for example polyoxyalkylene glycols, oxyalkylated phenolic resins, and oxyalkylated polyamines. The vinyl monomers which may be used in Burkis '379 include acrylic and methacrylic acids and their esters, vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate and the like, acrylonitrile, styrene and other vinyl aromatics, vinyl pyridine, vinyl pyrrolidone, acrylamide, maleic anhydride and its esters and half esters, and the like.
Burkis '628 discloses a vinyl-type inter-polymer having an overall carbon/oxygen atom ratio of about 2 to 4, which is preferably derived from two types of vinyl monomers: (1) at least one vinyl-type monomer present in the inter-polymer at about 50 mole % or greater and having a carbon/oxygen atom ratio of about 3 or less ("hydrophilic" monomer); and (2) at least one vinyl-type monomer present in the inter-polymer at about 50 mole % or less and having a carbon/oxygen atom ratio of about 3 or more ("hydrophobic" monomer). Typical examples are vinyl acetate/vinyl fatty ester copolymers and vinyl acetate/dialkyl maleate copolymers.
Other conventional demulsifiers are set forth in U.S. Pat. No. 4,678,599 (Fock et al.), issued Jul. 7, 1987. Fock et al. disclose various demulsifiers formed by copolymerizing one or several polyoxyalkylene ether(s) of allyl and/or methallyl alcohol with vinyl esters of lower carboxylic acids or mixtures of vinyl esters of lower carboxylic acids with up to 50 mole percent of esters or acrylic or methacrylic acid or ethers of allyl or methallyl alcohol and fatty alcohols, the quotient of the average molecular weight of the polyoxyalkylene ethers corresponding to their molar fraction and the number of moles of the compounds to be copolymerized being 20 to 200.
The present invention overcomes the many disadvantages of the aforementioned oxyalkylated demulsifiers and vinyl polymer demulsifiers, i.e., cost of ethylene oxide and increased vinyl polymer concentrations. The alkoxylated vinyl polymer demulsifiers of the present invention provide the following advantages: (1) relatively simple chemistry; (2) improved product performance; (3) synergistic effects when blended with some conventional emulsion breakers; (4) improvement in performance over non-alkoxylated vinyl polymers; and (5) since alkoxylated vinyl polymers are not totally dependent on ethylene oxide, it would be substantially insulated from price increases due to ethylene oxide which is not the case for oxyalkylated materials.
Additional advantages of the present invention shall become apparent as described below.